1. Field of the Invention
The present invention relates to a wafer processing method using two kinds of cutting blades.
2. Description of the Related Art
In cutting a wafer having a TEG (Test Elements Group), metal film, etc. in an area superimposed on each division line (street) from the front side of the wafer by using a cutting blade, the cutting blade is prone to be clogged, causing large chipping on the back side of the wafer. To cope with this problem, there is a case that a method called step cutting is adopted in dividing such a wafer. The step cutting includes the steps of using a first cutting blade having a large width (thick blade) to form a shallow groove as removing the TEG etc. and next using a second cutting blade having a small width (thin blade) to further cut the wafer along the above shallow groove, thereby dividing the wafer.
Further, in cutting a wafer by using a cutting blade, any factor such as heat generated during cutting may vary the amount (index amount) of indexing of the cutting blade in a direction perpendicular to each division line. If such a variation in index amount is left, the deviation of the cutting blade from each division line is gradually increased to cause a reduction in accuracy of processing of the wafer. To cope with this problem, there has been proposed a method including the steps of identifying the position of a previously formed groove on the basis of a characteristic target pattern exposed to the front side of a wafer and correcting the index amount in the case that the position of the groove is deviated from a proper position, thereby maintaining the processing accuracy for the wafer (see Japanese Patent Laid-open No. Hei 4-99607, for example).